1. Field of the Invention
This invention relates generally to padding materials that may be used for a variety of applications. More particularly, the invention relates to composite matrix and gel padding or cushions and a method of manufacturing such paddings and cushions.
2. Description of Related Art
The present state of the art for impact absorbtion is to use materials such as high density polystyrene foam in helmets or viscoelastic foams and gels in padding. There are a wide variety of high density polystyrene foam densities available, referred to herein under the brand name, Styrofoam®. Styrofoam® is a registered trademark of The Dow Chemical Company, P.O. Box 2166, Midland, Mich., 48641. Packing materials have very low densities of 1 pound per cubic foot, while higher density foams of 3 pounds per cubic foot can be found in helmet liners. Visocelastic foams and gels vary in density from 5 pounds per cubic foot in some foams to as much as 65 pounds per cubic foot in gels. Low density foams begin to crush or compress with lower amounts of applied force compared to high density foams. The resistance to compression in gels is a function of the hardness as determined by the Shore durometer rating. Gels with high Shore values behave more like rigid solids, while those with low Shore values behave more like viscous liquids. It is this inherent resistance to compression that determines how much acceleration an object is subject to when it strikes the surface of an impact absorbing material. The various materials employed for this purpose thus far have shown wide-ranging capabilities to attenuate accelerative forces at highly variable velocity profiles.
Tissue injury due to sustained compressive forces or rapid acceleration/deceleration has been well documented. Various materials have been employed to reduce the amount of tissue damage (i.e., pressure sores, concussions, etc.) that can occur when there is sufficiently high force or acceleration on the body. Materials such as Styrofoam® (a light, resilient foam of polystyrene available from Dow Chemical Co.), viscoelastic polyurethane foam, and polyurethane gel have been used as padding materials. One problem with the design of some of these padding materials has been the lack of suitable testing to determine the amount of protection afforded by the material in terms of G-acceleration or deceleration. Another problem is the weight and cost of the material, particularly for polyurethane gel. Some inventors have included measurements on the amount of force or acceleration protection that the padding material provides. While this information is helpful it does not fully assess the potential effects of acceleration alone, or of force, which is mass dependent, on body tissues. In the case of head injury the present American Society for Testing and Materials (ASTM) standards for helmets do not provide adequate protection from the effects of acceleration and force. However, it is difficult to change conventional helmet structural designs because of the legal liability resulting from head injuries involving helmets. Consequently, it is necessary to develop new padding materials that are able to provide a superior level of protection from acceleration and the effects of mass on bodily tissues.
Inherent protection of bodily parts from compressive forces, acceleration and deceleration is effected by integument, adipose, and skeletal tissues. The skeletal system provides protection from penetration and compression of internal organs, but has little ability to mitigate the effects of acceleration on the organ system. Protection from acceleration is effected by the integument and adipose tissues due to their ability to sustain stretching and compression. Various forms of polyurethane have demonstrated excellent properties in this regard, particularly the gel and viscoelastic foam formulations. One problem with the use of such materials is that no one form is able to provide the broad range of characteristics that may be required in a protective material.
The background art is further characterized by U.S. Pat. Nos. 7,254,843 to Talluri; 7,141,032 to Flam et al.; 7,076,811 to Puchalski; 7,062,795 to Skiba et al.; 6,704,943 to Calonge Clavell; 6,070,271 to Williams; 6,026,527 to Pearce; 6,025,067 to Fay; 5,947,918 to Jones et al.; 5,749,111 to Pearce; the disclosures of all of which are incorporated by reference as if fully set forth herein.
Thus, it would be advantageous to have composite padding materials that exhibit similar properties to those of skin, integument and adipose tissues of the human body. It would be advantageous if such a composite padding material was also lightweight and easy to manufacture.